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Full text of "The Cambridge Natural History"

CHAPTER   XVI
INSECTIVORA-----CHIROPTERA
Order XL    INSECTIVORA.
THE Insectivora1 are an order of mammals to which it is \
quote Professor Huxley) "exceedingly difficult to give a definitio]
They are, however, none of them large animals, and most of the
are nocturnal in habit—two circumstances which may have hi
something to do with their survival from past ages, as may ha
also their modification  to so many and  diverse modes  of lift
for  everything points to the antiquity of the group.     They ai
for instance, more or less plantigrade.     The snout is general!
long, and is  often prolonged into a short proboscis.2     There ;
a   tendency   for   the   teeth   to   be   of a   generalised   type,  an
their   number   is   often    the    typical   mammalian    forty-fou]
Moreover, trltuberculate   teeth,  which are  certainly an  ancien
form  of tooth, are common; and indeed the  Insectivora  of tin
southern regions of the globe, e,g. Centetidae, Solenodontidae, anc
Chrysoehloridae, have the most prevalent trituberculism, a fact
which is of importance in considering the age of the animal life
of these regions of the world.     The limbs are, as a rule, provided
with  five   digits.      The hemispheres   of the  brain  are   usually
smooth, and do not   extend  over  the  cerebellum.     The   palate
is often fenestrate as  in the Marsupials, and as in that group
the lower jaw is sometimes inflected.     But  the latter character
also occurs in the Sea-lions and elsewhere.    Clavicles are present,
as a rule, but not in Potamogcde.
1  See especially Dobson, A Monograph of the Insectivora, London, 1886-90,
2  Even in the Otter-like Potamogale the upper jaw, though hroad and flat,
projects considerably beyond the lower.